3.9 GHz, 3rd Harmonic 4-Cavity Module Status H Edwards/E Harms - - PowerPoint PPT Presentation

3.9 GHz, 3rd Harmonic 4-Cavity Module Status

H Edwards/E Harms Fermilab

May 18-19, 2009 DOE SRF Review 2

Outline 3.9GHz Module

• What is it and what will it do?

– It is not in SRF B&R category (B&R 15.02.011 General Acc Dev)

• Why do it & What has it done for Fermilab?
• Progress, Accomplishments, History

– Technical progress

• The steps: Design, Fabrication, Process, Vertical test, Dress, Horizontal test,

Module assembly, Infrastructure

– Associated systems - LLRF

• Lessons Learned and Problems encountered
• Schedule - Looking Forward
• Collaboration - Future Collaboration?
• Future at Fermilab?
• Conclusion

May 18-19, 2009 DOE SRF Review 3

The 3.9 cavity module -What is it -what will it do? The 3.9 cavity module -What is it -what will it do?

• The 3.9 GHz module, ACC39, will be installed in the DESY FLASH injector

just after the 1.3GHz ACC1 (first) cryo module.

• It will be used in conjuction with this module in order linearize the bunch

energy vs. time over the bunch length.

• This in turn should make “bunch compression” to very short bunches

with high peak currents more efficient, or a more controlled longer bunch charge distribution.

• The SASE FEL operation should become more efficient and stable seeded
• peration (sFlash) possible.
• This is an important proof of principle not only for FLASH and XFEL but

also for accelerator-photon physics, and a learning experience.

• The control of the phase and amplitude of the 1.3-3.9 module pair will be

difficult and very important.

May 18-19, 2009 DOE SRF Review 4

Bunch Compression with 3.9 GHz Module

From P Piot

After acceleration w/o After compression w/o With 3rd harmonic

From M Dohlus et al

Short bunch Flat bunch ~250 fs σ

May 18-19, 2009 DOE SRF Review 5

Why Do It & What Has It Done for Fermilab?

• The 3.9 effort is part of a collaboration with DESY.
• In this collaboration DESY has advised Fermilab on many of the

aspects of SRF development and has supplied design and assembly information.

• DESY provided for Fermilab a 8 cavity module at 1.3 GHz. This

Module is being installed in the NML facility.

• The 3.9 GHz module has been/will be a learning experience for

FNAL in all aspects of beta 1 SRF cavity and module design through commissioning.

• Successful completion will clearly show Fermilab’s growing

competence and abilities in SRF technology.

• It is important that we learn and benefit for our experiences and

“Lessons Learned”.

May 18-19, 2009 DOE SRF Review 6

3.9GHz Overview Photos 3.9GHz Overview Photos

May 18-19, 2009 DOE SRF Review 7

Infrastructure for 3.9 Infrastructure for 3.9

• Some old and some new

– Old - A0 SRF R&D Infrastructure – Modest, built up over the years

• Soft wall clean room
• UV water & Ultrasonic bath
• High Pressure Rinse sufficient for small cavities
• Vertical test (short dewar)
• Cryo - dewar fed and recovered to CHL
• RF systems (1.3 & 3.9)

– New - set up and used for 1.3 GHz

• Horizontal Test Stand (HTS) at Meson (MDB)
• String and Coldmass assembly at MP9
• Module assembly at Industrial Center (ICB)

– Some steps very time inefficient

• Welding at Sciaky (or JLab) and weld preparations
• Chemistry at ANL (conflict with their work)

May 18-19, 2009 DOE SRF Review 8

Cavity Fabrication Steps Cavity Fabrication Steps

• Documents on Cavity and Helium Vessel Fabrication and Welding

by M. Foley, et al

– 3.9 GHz Cavity Fabrication Specification

• Material
• Blanks for half cells
• Fabrication of Components
• End Assemblies
• Welding of Cavity
• Final Test of Cavity

– Procedures for Welding Helium Vessels to 3.9 GHz Cavities

• Preparation for Electron Beam welding
• Electron Beam Welding
• Preparation for TIG Welding
• Final TIG welding
• E-beam Weld Parameters
• TIG Weld Parameters

May 18-19, 2009 DOE SRF Review 9

Fabrication and Processing Steps

• Table of processing steps by A. Rowe

– About 200 steps after fabrication

• Outline

– Preliminary Processing Sequence

• Preliminary Preparation
• External Surface Preparation
• Internal Bulk Surface Preparation
• Hydrogen Degasification
• RF tuning

– Vertical Test Processing Sequence

• Internal Surface Preparation
• 1st Vertical Test
• 2nd Vertical Test

– Titanium Helium Vessel Welding – Horizontal Test Processing Cycle

May 18-19, 2009 DOE SRF Review 10

String and Module Assembly Steps

• Assembly Travelers by T. Arkin, M. McGee, D. Olis, et al

– Assembly QA Traveler – Cavity String Assembly – Cold Mass Assembly Parts 1-3 – Final Assembly Traveler – Shipping Document – Warm Coupler Assembly Document

May 18-19, 2009 DOE SRF Review 11

Warm/Low power RF Measurements

• T. Khabiboulline

modes

May 18-19, 2009 DOE SRF Review 12

Summary of Last Vertical Tests - Design 14MV/m Summary of Last Vertical Tests - Design 14MV/m with and w/o HOM antennae with and w/o HOM antennae

1.8K

• C3 (2008_07_22 with HOM ant)

– Q @14 MV/m 2.2e9 – Max Gradient 17.6 MV/m, Q 1.2e9

• C3 (2008_08_27 no HOM ant)

– Q @14 MV/m 5.2e9 – Max Gradient 22.8 MV/m, Q 1.3e9

• C5 (2007_08_22 no HOM ant)

– Q @14 MV/m 5.1e9 – Max Gradient 25 MV/m, Q 2.0e9

• C5 (2008_10_04 with HOM ant)

– Q @14 MV/m 4.1e9 – Max Gradient 17 MV/m, Q 3.7e9

• C8 (2007_11_08 no HOM ant)

– Q @14 MV/m 4.9e9 – Max Gradient 24.2 MV/m, Q 1.5e9

• C8 (2008_12_03 with HOM ant)

– Q @14 MV/m 2.8e9 – Max Gradient 20.4 MV/m, Q 1.3e9

2.0K

• C3 (2008-08_27 no HOM ant)

– Q@14MV/m 2.6e9 – Max Gradient 20.3 MV/m, Q 1.7e9

• C7 (2008_02_07 no HOM ant)

– Q @14 MV/m 2.3e9 – Max Gradient 25.1 MV/m, Q 1.3e9

• C7 (2008_10_27 with HOM ant)

– Q @14 MV/m 2.0e9 – Max Gradient 24.8 MV/m, Q 1.2e9

May 18-19, 2009 DOE SRF Review 13

3.9 GHz Cavity Vertical Tests - 1

May 18-19, 2009 DOE SRF Review 14

3.9 GHz Cavity Vertical Tests - 2

May 18-19, 2009 DOE SRF Review 15

Cav 3,5,7,8 Horizontal Test Results at HTS

F3A3 22.5 MV/m F3A5 22.5 MV/m F3A7 26.3 MV/m F3A8 24 MV/m

Design Gradient 14MV/m

May 18-19, 2009 DOE SRF Review 16

• 2002

TESLA Facility Phase 2 Report with 3.9 GHz module for bunch compression (TESLA-FEL 2002-01)

• 2002-3

Cavity design documents (TESLA-FEL 2002-05, 2003-01/FNAL TM 2210)

• 2005

DESY-FNAL MOU on 3.9 module

• 2006, 03-06

C1,C2 failures, Multipacting & HOM wall thickness

• 2006, 08

F3A3 fabrication finished- first usable cavity

• 2007, 05

F3A3 good vertical test after HOM formteils cut, 24MV/m

• 2007, 10

F3A5 vertical tests with HOM feed-throughs complete 19MV/m

• 2008, 02-09

F3A5 in horizontal test stand (HTS)

• 2008, 04

F3A5 achieved 22.5MV/m in HTS

• 2008, 12

F3A7 last cavity of four removed from HTS

• 2009, 01

String assembled in MP9 Clean Room

• 2009, 02

Cold mass to ICB

• 2009, 04

Module finished and shipped to DESY

3.9 Schedule Highlights - 3.9 Schedule Highlights - past ast

2002 to 2009 - start to ship - for module tests at DESY

May 18-19, 2009 DOE SRF Review 17

Problems & Lessons Learned - 1

• Technical issues

– HOM design and multipacting - 1-post redesign for F3A7, F3A8 – HOM antennae feedthroughs - followed JLab type design – Titanium Helium vessel weld design, welding and Titanium pipe welding – Design mistakes - e.g. thickness of HOM can top

• Infrastructure issues

– e- Beam welder availability – BCP etch availability, FNAL & ANL – HTS commissioning – Maintenance of effective CR, HPR, and Cryo systems at A0

• Procedural issues

– Pressure vessel testing and Engineering note, ORC

May 18-19, 2009 DOE SRF Review 18

• Major delays (~3 months or more)

– Understanding and Redesign of HOM antennae

• Re-prototyping of the e- beam welding parameters for HOMs (DESY).

– Redesign and rebuilding of the Ti Helium vessels

• Certification of the welds and welding procedures.

– E beam welding done at Sciaky, typically 1 day a week to 1 day/2

• weeks. Not always available, others scheduled
• Preparation for remote welding cumbersome and time consuming.
• Sciaky sold machine making ~6 month delay as new machine installed

and new parameters determined.

– BCP infrastructure availability

• FNAL - only minimal availability for etch of edges of half cells, etc

prior to welding. ~ 5 month delay while facility was improved and recertified.

• ANL - ANL collaboration very important. Used their existing G150

system, but not always available.

Problems & Lessons Learned - 2

May 18-19, 2009 DOE SRF Review 19

Problems & Lessons Learned - 3

– HTS Commissioning

• Understanding the Horizontal Test cryostat and its cryogenic
• peration (temperature profiles) took some time.
• Re-work of HTS components & time to get leak tight system.
• These were coupled with the delay in getting a sign-off to test the

first (F3A5) 3.9 GHz cavity and subsequent cavities.

– Engineering Note Authorization

• Lack of appreciation by the design engineers that the system had

to be designed and documented as much as possible following code procedures. Issue for both for DESY and FNAL.

• Fermilab is learning to deal with the safety aspects of SRF testing

(non-ASME materials, etc.). The 3.9 GHz effort, especially the HTS step, played a pioneering role in the format and content of Engineering notes and approval to cooldown and power test SRF

• cavities. At times a frustrating process (~6 months for HTS

approval), but the need is also understood. Organizationally, Fermilab is now better poised and taking strategic steps for future

• perations.

May 18-19, 2009 DOE SRF Review 20

Problems & Lessons Learned - 4

• Re-build

– HOM antennae feed-throughs – Module piping – Helium vessel

• Re-work

– Horiz test cryostat top flange, liquid level monitor – Input couplers plating and tolerances

• Re-test cavities in vertical test

– Vertical testing included: Bare cavity, with HOM antennae, welded in helium vessel, with helium vessel and HOM antennae, 2K and 1.8K.

• not all cavities had all vertical tests

– Time lost if test unsuccessful. – Cavity # vertical tests

• C5

4

• C3

10

• C7

4

• C8

8

• C4

16

• C6

17

May 18-19, 2009 DOE SRF Review 21

Accomplishments and Lessons Learned

• Accomplished or Learned

– All the steps in design, fabrication, process, test, and assembly of a multi-cavity module. – Test and Assembly infrastructure:

• Vertical Test stand improvements
• Coupler Conditioning stand
• HTS and its control room - RF, Cryo, Vac, Interlocks, etc.
• String and Module Assembly infrastructure used at MP9 & ICB
• Learned

– The necessity of complete and accessible infrastructure tools for efficient development, chemistry, welding, etc.

• Specifically

– The importance of prototype testing e.g. multipacting – Fabrication and Welding of Titanium – Vendor capabilities and qualification - HOM feedthroughs, input couplers, Helium vessels, etc. – The necessity for Fermilab to act in an efficient, consistent, and coherent way vis a vis balance in technical progress and its required documentation associated with proceeding with technical tests or procedures.

May 18-19, 2009 DOE SRF Review 22

Still to Do Still to Do

• Spare cavities

– Can we make F3A4 & F3A6 work? So far have not been able to get good Vertical dewar test results, MULTIPACTING. Recent F3A4 HTS test to 17MV/m. – HTS test of F3A4 underway - do we have a fundamental problem with the HOM 2-post formteils? Will that be a problem for the Module cavities F3A3, F3A5? – Need to complete a spare - F3A9

• Summary Report of RF tests and measurements for each cavity (in

progress)

– History overview for assembly, process, measure and test – Warm and mechanical measurements – Vertical test summary – Horizontal test summary – Final tests.

• Summary Report of Technical Designs (in progress)

– Accelerator physics use of 3.9 GHz module – RF design of cavities, input couplers, HOM couplers, – Thermal analysis – Cavity assembly and processing steps.

May 18-19, 2009 DOE SRF Review 23

Update on Module after Arrival at DESY

• Transportation shock log data good, maximum 1.2 g differential.
• Vacuum was maintained during transport. String is leak-tight (10-8

Torr at pump).

• One heat shield interference found and corrected (80K coupler

shield to 4K module shield).

• Survey comparison FNAL->DESY exellent:

– Cavity targets as a group comparison, max difference 0.16mm – Relative to cold mass max difference 0.28mm – Measurement accuracy ~0.15mm – Gate valve motion ~0.7 mm.

• Some cavity support bearing housings, “C channels”, are out of

position, others are not accessible in the module to check. Likely

• ccurred during string assembly/alignment. The present plan is to

remove the cold mass at DESY shortly and check, replace/reposition (as needed) the channels and bearings - time estimate 2.5 weeks.

May 18-19, 2009 DOE SRF Review 24

3.9 Schedule Highlights - Future

We must still show that the cavities work in the module at DESY test facility and TTF/FLASH.

User operation Summer ‘10 Beam commissioning in FLASH Apr - June ‘10 Technical commissioning of ACC39 in FLASH March ‘10 ACC39 installation in FLASH Dec 09 - Feb ‘10 FLASH shutdown Sept 09 - Feb ‘10 Test ACC39 at CMTB Oct - Dec ‘09 Installation and check out of module at CMTB Oct - Nov ‘09 Preparation of Cryo Mod Test Bench (CMTB) at DESY for 3.9 test May - Sept ‘09 Module inspection after delivery to DESY April - May ‘09

May 18-19, 2009 DOE SRF Review 25

Collaboration Collaboration

• ANL

– Argonne has been of considerable help over the years in the area of cavity processing (BCP) – Close collaboration with ANL will continue.

• Cornell

– Cornell/Padamsee was instrumental at getting us started at A0 on 3.9GHz and more recently

• n 1.3 GHz development. Collaboration continues.
• DESY

– The collaboration with DESY has been critical for Fermilab to learn SRF and module technology. – DESY has been an invaluable aid during the 3.9 GHz effort with cavity design, review of the module, welding HOM parts, LLRF, helium vessel, …. – We hope that collaboration can continue in other areas and in particular in LLRF and HOM measurement developments for 3.9 GHz operation at FLASH, and that further roles in FLASH and XFEL can be identified and supported. – There is much to be learned by a close relationship as XFEL proceeds.

• JLab

– JLab people have been very helpful with advice and in the actual fabrication of the cavities. – They helped measure, repair and weld cavity cells. This was critical when the work at Sciaky was interrupted. – They freely discussed their HOM feedthrough design concepts. – The collaboration with JLab is continuing.

May 18-19, 2009 DOE SRF Review 26

Other Things Other Things

• LLRF

– The Low Level RF for the 3.9 module will be critical, with very difficult regulation and stability requirements. – Fermilab should work with DESY on this problem as we now have 3.9 LLRF system hardware and software. – The demands of the 3.9/1.3 FLASH system will be a valuable challenge. – Fermilab is also working on LLRF for the FLASH 9ma test. – HOM beam position development is started for 3.9 signals.

• 3.9 future at FNAL (both accelerating and deflecting mode)

– 3.9 cavities would benefit research at both the A0 Photoinjector and at NML. – Though 3.9 cavities are planned for NML, it is not clear when the resources will be available for work to proceed.

May 18-19, 2009 DOE SRF Review 27

Conclusions

• The 3.9 module has been an important and fundamental learning

experience for FNAL in all areas of SRF technology.

• This is the 1st 3.9 GHz module built anywhere. DESY acknowledges

this new expertise.

• Cooperation across the Fermilab organization was vital to

accomplish this. New players have been recruited and trained.

• Successful lasing results from FLASH will be an important step of

R&D to the accelerator field in general and illustrates the importance

• f accelerator developments & applications across different end user
• facilities. (e.g. Hi Energy, Nuclear, Materials,…)
• Charge 1

– The 3.9 GHz module completion has been a major accomplishment with a significant part carried out in the last 2 years. – The existing capabilities have been commissioned and effectively utilized.

• Charge 4

– The development, assembly and test of the 3.9 cavities/module would not have been possible without extensive collaborative efforts and support from other laboratories.

May 18-19, 2009 DOE SRF Review 28

Backup Backup

• Photos
• Parameters
• HOMs
• LLRF
• ORC (Operational Readiness Review)

– http://ilc- dms.fnal.gov/Workgroups/CryomoduleDocumentation/3 rd-Harmonic-Cryomodule-for-DESY/

May 18-19, 2009 DOE SRF Review 29

Parameters Parameters

Parameter List for the 3.9 GHz Cavities W. - D. Moeller, 14.08.02 Type of structure standing wave Accelerating mode

• mode

Voltage 20 MV Accelerating gradient, Eacc 14 MV/m Phase

• 179°

Cell to cell coupling 3.97 % Stored energy 1.2 J Frequency 3.9 GHz cavity 9 - cell R/Q [=U2/( W)] 375 Ohm [750 Ohm] Epeak/Eacc 2.26 Bpeak/Eacc Bpeak @ Eacc = 14 MV/m 4.86 mT/ (MV/m) 68 mT Tuning range 3900 ±1 MHz ∆f/∆L 2.39 MHz/mm Lorenz force detuning constant KLor 6 Hz/(MV/m) Number of cavities 4 (+2 spares) Beam current 9 mA Qext 13.0 x 105 Total Energy 20 MeV Bandwith 4.1 kHz Forward power 11.5 kW Coupler power (per coupler) 45 kW BBU limit for HOM, Qext < 1.0 x 105 Active length of 9 cells 345.96 mm 2 x taper in beam pipe 2 x length of beam pipe (for power- and HOM- couplers) 159.94 mm Cavity overall length 505.9 mm Bellow length 102 mm Total length needed (end flange to end flange) 2329.70 mm

May 18-19, 2009 DOE SRF Review 30

Old and New HOM 3.9 antennae

Cavities 3 and 5 are old two post design trimmed Cavities 7 and 8 are new one post design

May 18-19, 2009 DOE SRF Review 31

LLRF development 1.3 and 3.9 GHz

J Branlard, G Cancelo, B Chase, U Mavric, A Paytyan (students) LLRF control

– Example of development work that is aided by the availability of the photoinjector to test systems with Rf and beam

• Shown is 3.9GHz acc system

– RMS Amplitude ~2.5e-4 – RMS Phase ~0.05 deg

System developed in collaboration with DESY, but is FNAL realization.

– Rf control will be basic to all new linac developments (e or p)

• Also 3.9 GHz SRF deflecting

cavity excellent for bunch length measurement

May 18-19, 2009 DOE SRF Review 32

ORC ORC

3rd Harmonic Cryomodule for DESY

Up one level

This folder contains documentation for the 3rd Harmonic Cryomodule for DESY. ORC Review Documents and Commentary This folder contains presentations and notes from the Operational Readiness Clearance (ORC) review for the 3.9 GHz Cryomodule. ACC39 Introduction, Parameters, and Specifications This is a combined introductory document containing a summary of Fermilab and DESY responsibilities for ACC39, a top level parameter list for the cryomodule, pressure specifications, and other requirements. 3.9 GHz cryomodule hazard/risk analysis As part of the Fermilab Technical Division Operational Readiness Clearance (TD-ORC) documentation requirements, a hazards/risk analysis has been prepared for the 3.9GHz Cryomodule, ACC39. This analysis identifies the hazards associated with ACC39 installation and operation at DESY and presents appropriate mitigating actions which, when implemented, either eliminate or reduce risks to acceptable levels. 3.9 GHz Cryostat Pressure Specification The document includes the specification from DESY for the 3rd harmonic cryostat with some commentary and Fermilab-DESY conclusions. Vacuum Vessel Engineering Note and Documents This folder contains the signed engineering note and associated documents for the 3.9-GHz cryomodule vacuum vessel. Helium Vessel Engineering Note for 3.9-GHz Dressed Cavity, #5 This folder contains the engineering note and all associated electronic files for the 3.9-GHz dressed SCRF cavity, #5. For all these engineering notes, relief valve details and venting analysis refer to Fermilab's horizontal test cryostat. Old versions of documents have been moved to the folder "Old versions of documents". Helium Vessel Engineering Note for Cavity #3 This folder contains the helium vessel engineering note for Cavity #3. Associated documents (material certifications, welder certifications, weld procedure) are also in this folder. Helium Vessel Engineering Note for Cavity #8 This folder contains the helium vessel engineering note for Cavity #8. Associated documents (material certifications, welder certifications, weld procedure) are also in this folder. Helium Vessel Engineering Note for Cavity #7 This folder contains the helium vessel engineering note for Cavity #7. Associated documents (material certifications, welder certifications, weld procedure) are also in this folder. Dressed Cavity Drawings

May 18-19, 2009 DOE SRF Review 33

ORC pg2 ORC pg2

ACC39 Interface Specification This document specifies the interfaces between ACC39 and the installation at DESY at the Cryomodule Test Bench (CMTB) and then in TTF/FLASH. Cryomodule Piping Engineering Note Piping engineering note and associated documentation 3.9 GHz cryomodule piping mechanical loads This document contains an analysis of mechanical loads on the piping in ACC39 as installed in FLASH at DESY. Lateral loads, axial loads, and lateral elastic pipe instability are all analyzed. (updated 11 Feb 2009.) Low temperature stresses This document summarizes the calculated cold stresses and allowable cold stresses in the helium vessels and cavities to demonstrate the 4.0 bar cold Maximum Allowable Working Pressure (MAWP). This supplements the helium vessel engineering notes since those documented a 2.0 bar warm or cold MAWP. Cavity Production Flow Chart for the 3.9 GHz Cavities Flow chart of the cavity production process for all the 3.9 GHz cavities, including branch points for their difgerences. Niobium mechanical properties This document surveys published niobium mechanical property data. Included are the rationale and conclusions for high RRR, heat treated, niobium allowable stresses. Cryomodule shipping specification Shipping specification, detailing packaging and shipping responsibilities for the 3rd harmonic cryomodule transportation to DESY. Helium Vessel Engineering Note for Cavity #4 (spare cavity) This folder contains the engineering note and associated documents for Cavity #4. (Log in to view and download documents in this folder.) Old versions of documents Old versions of 3.9 GHz cryomodule documents are stored here for reference. (Log in to view and download documen

May 18-19, 2009 DOE SRF Review 34

Cavity fabrication,BCP, HPR, Vertical Test

Weld BCP etch Hi Press Rinse Vertical test & dewar Vertical test control area Bare 3.9 cavity

May 18-19, 2009 DOE SRF Review 35

Helium vessel welding Dressed Cavity to HTS

May 18-19, 2009 DOE SRF Review 36

The string to cold mass The string to cold mass

May 18-19, 2009 DOE SRF Review 37

ICB Module Assembly ICB Module Assembly

Ready to Ship Arrived DESY Coupler Assembly test

May 18-19, 2009 DOE SRF Review 38

The people The people

A0 group MP9 group The whole group

May 18-19, 2009 DOE SRF Review 39

Collaboration Collaboration

• ANL

– Argonne has been of considerable help over the years in the area of cavity processing (BCP) – Close collaboration with ANL will continue.

• Cornell

– Cornell/Padamsee was instrumental at getting us started at A0 on 3.9GHz and more recently

• n 1.3 GHz development. Collaboration continues.
• DESY

– The collaboration with DESY has been critical for Fermilab to learn SRF and module technology. – DESY has been an invaluable aid during the 3.9 GHz effort with cavity design, review of the module, welding HOM parts, LLRF, helium vessel,….. – It is unfortunate that Fermilab does not want to continue collaboration on 3.9 GHz with the XFEL as Fermilab has invested so much effort in the design and development. It would have been natural to take on this high visibility XFEL effort. – We hope that collaboration can continue in other areas and in particular in LLRF and HOM measurement developments for 3.9 GHz operation at FLASH, and that further roles in FLASH and XFEL can be identified and supported. – There is much to be learned by a close relationship as XFEL proceeds.

• JLab

– JLab people have been very helpful with advice and in the actual fabrication of the cavities. – They helped measure, repair and weld cavity cells. This was critical when the work at Sciaky was interrupted. – They freely discussed their HOM feedthrough design concepts. – The collaboration with JLab is continuing.